1. Field of the Invention
The present invention generally relates to modulators, and more particularly, to an electro-optical modulator.
2. Description of Related Art
Presently, the optoelectronic technology employs substrates made of different semiconductor materials in producing integrated optoelectronic components for light emitting, light modulation, light detection, or light guiding. For example, a typical silicon material is featured with a relative low loss in light transmittance. For this reason, related research with respect to silicon material concerns more about applications of optical features thereof, for example an optical waveguide component.
Further, a silicon-on-insulator (SOI) component is configured by depositing a layer of monocrystalline silicon having a thickness of 0.2 to 100 microns on a silicon substrate, and a dielectric layer having a thickness of 0.25 to 3 microns is disposed between the substrate and monocrystalline silicon for isolating electric effect so as to reduce the power consumption, and decreasing current loss and injunction resistance so as to accelerate a processing speed of the IC. In other words, the SOI component is adapted for manufacturing products requiring for lower power consumption. As such, SOI components are often employed in equipment for lower power consumption, such as cellular phones, or watches. In order to more effectively exert the advantage of high speed operation, the SOI components are more often employed in low power portable communication devices, smart power switches, wideband local network broadcasting networks, micro-optoelectronic components for optical signal processing, and micro electromechanical components.
Presently, an optoelectronic component made of silicon material usually achieves a high speed modulation by free carrier plasma dispersion effect. According to the free carrier plasma dispersion effect, a refractive index of the material is changed by implanting carriers therein, and a structure of Mach-Zehnder interferometer configured by the material is adapted for a mechanism of high speed modulation.
In optical communication system, data are usually inputted into optical fibers via an electro-optical modulator. However, because of the ultra bandwidth of the optical fiber, and the demultiplexing function for the operating wavelength and frequency, presently using 10 Gb/s electro-optical modulators doesn't satisfy the requirement of application. In order to satisfy the coming OC768 optical communication broadcasting, a modulation speed greater than 30 GHz is critical and very much desirable. Most of the effective semiconductor electro-optical modulators are designed with the operation principle according to the free carrier plasma dispersion effect. Specifically, a modulation structure of a forward bias PIN diode or a modulation structure of a metal oxide semiconductor (MOS) capacitor can achieve a frequency bandwidth of 2 GHz only. A modulation structure of a reverse biased PN junction can achieve a modulation speed frequency band of 20 GHz at most. Accordingly, for achieving a faster data transmission speed, an electro-optical modulator having a faster modulation speed and a lower power consumption is desired for expediting the development and application of the enterprise.